Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 221844
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
244 PM EDT TUE JUL 22 2014

.SYNOPSIS...
EXPECT A BRIEF RETURN TO MORE TYPICAL SUMMER WEATHER ON WEDNESDAY
BEFORE A FRONT APPROACHES AND MOVES ACROSS THE REGION ON THURSDAY.
THE PASSAGE OF THE FRONT WILL NOT BRING COOLER AIR...BUT IT SHOULD
BRING DRIER AIR FOR FRIDAY AND INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AT 230 PM EDT TUESDAY... FOR THE REMAINDER OF THE AFTERNOON AND
EVENING... SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL PERSIST
IN A MOIST BUT ONLY MODESTLY UNSTABLE AIR MASS. NO SIGNIFICANT
SURFACE FEATURES EXIST IN THE CWA TO PROVIDE AN OBVIOUS FOCUS FOR
CONVECTIVE DEVELOPMENT. EXPECT SHOWERS TO DRIFT SLOWLY TO THE
NORTHWEST WITH PERHAPS A SLIGHT PREFERENCE FOR ENHANCEMENT AND BEST
COVERAGE THIS EVENING IN AREAS WITH UPSLOPE FLOW. WINDS ALOFT
THROUGH THE EVENING WILL REMAIN QUITE LIGHT IN THE COL REGION OF THE
MID AND UPPER TROPOSPHERIC HEIGHT FIELD... SO SLOW MOVEMENT OF
CONVECTIVE CELLS IS LIKELY. OVERNIGHT FOG IS POSSIBLE... BUT MODELS
AT THIS TIME ARE NOT DEFINITIVE IN INDICATING WIDESPREAD LOW
VISIBILITY CONDITIONS. NONETHELESS... THE POTENTIAL BEARS WATCHING
OVERNIGHT. THE PRIME AREA FOR SIGNIFICANT FOG WILL BE IN THE
MOUNTAIN VALLEYS AND ACROSS THE NORTHERN FOOTHILLS INTO THE
NORTHWEST PIEDMONT OF NC.

UPPER LEVEL PATTERN ACROSS THE AREA WILL UNDERGO A TRANSITION
TONIGHT AND WEDNESDAY. THE CUTOFF LOW OVER GULF COAST STATES WILL
CONTINUE A SLOW DRIFT TO THE WEST AND HEIGHTS WILL FALL TO OUR NORTH
IN ADVANCE OF SIGNIFICANT TROUGH DIGGING INTO THE EAST. AS TROUGH
HEADS ACROSS THE GREAT LAKES TOWARD THE ATLANTIC COAST... THE
SURFACE RIDGE THAT HAS EXTENDED FROM THE MID-ATLANTIC INTO THE
CAROLINAS FOR A COUPLE OF DAYS WILL DISAPPEAR. IN ITS PLACE WE ARE
LIKELY TO HAVE A LEE TROUGH RETURN TO THE PIEDMONT PORTION OF THE
CWA BY WEDNESDAY AFTERNOON. THE FALLING HEIGHTS AND APPROACHING
DIGGING TROUGH WEDNESDAY AFTERNOON WILL BE ACCOMPANIED BY A WESTERLY
WIND FLOW ALOFT AND SOUTH TO SOUTHWEST WIND IN THE BOUNDARY LAYER.
THE RESULT WILL BE A RETURN TO A MORE DIURNAL PATTERN OF CONVECTION
WITH THE HIGHEST POPS OVER AND NEAR THE HIGHER TERRAIN. WITHOUT A
MAJOR CHANGE IN AIR MASS... SIGNIFICANT TEMPERATURE CHANGES WILL NOT
OCCUR. TUESDAY MORNING LOWS ARE EXPECTED TO BE NEAR 70 WITH 60S IN
THE MOUNTAIN VALLEYS. WEDNESDAY AFTERNOON TEMPERATURES WILL BE
BETWEEN 85 AND 90 EXCEPT IN THE LOWER AND MIDDLE 80S IN THE MOUNTAIN
VALLEYS.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM EDT TUESDAY...ALL NUMERICAL GUIDANCE IS FORECASTING A
STRONG SHORT WAVE TO MOVE THROUGH THE GREAT LAKES WED NIGHT INTO THU
WHICH WILL DRIVE A SURFACE COLD FRONT SOUTHEASTWARD INTO THE
SOUTHEAST STATES. THE NAM AND GFS HAVE SETTLED ON SIMILAR TIMING
IN REGARD TO THE FRONT WITH BOTH MODELS BRINGING IT TO JUST NW OF
THE NC MOUNTAINS BY 12Z THU...AND THEN BRINGING IT ACROSS THE
MOUNTAINS INTO THE LOWER PIEMDONT BY THURSDAY EVENING. THE FRONT IS
THEN FORECAST TO CLEAR THE AREA BY MIDNIGHT. A DRYER AND MORE STABLE
AIR MASS IS EXPECTED TO OVERSPREAD THE AREA ON FRIDAY AS HIGH
PRESSURE RIDGES SOUTHEASTWARD FROM THE OHIO VALLEY.

IN REGARD TO SENSIBLE WEATHER...SOME LINGERING SHOWERS AND STORMS
MAY BE OVER THE AREA WED EVENING...BUT THEY SHOULD DISSIPATE WITH
LOSS OF HEATING WED NIGHT. HOWEVER...WILL NEED TO RAMP POPS UPWARD
LATE THURSDAY NIGHT AS SOME PREFRONTAL SHOWERS MAY REACH THE
MOUNTAINS BY SUNRISE THURSDAY. WILL CONTINUE TO ADVERTISE LIKELY
POPS IN PORTIONS OF THE MOUNTAINS AND ALSO IN NC PIEDMONT ON THU
AFTERNOON...BUT CONVECTION SHOULD BE SCATTERED ELSEWHERE AS WINDS IN
PROFILES ARE DECIDELY DOWNSLOPE IN NATURE. THERE SHOULD BE PLENTY OF
INSTABILITY THU AFTERNOON WITH CAPES POOLING TO 1500-2000J OVER THE
PIEMDONT. HENCE...A FEW SEVERE STORMS ARE POSSIBLE. WILL FORECAST
DECREASING POPS THU NIGHT AND THEN A DRY DAY ON FRI. MAX TEMPS WILL
BE BELOW CLIMO BOTH THU AND FRI IN THE MOUNTAINS...BUT NEAR CLIMO
OUTSIDE THE MOUNTAINS ON THU AND THEN ABOUT A CATEGORY BELOW CLIMO
ON FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...THE MEDIUM RANGE GUIDANCE SUGGESTS THAT THE
EASTERN U.S. TROUGH WILL FLATTEN AS HEIGHTS RISE IN RESPONSE TO
ANOTHER STRONG UPPER WAVE DIGGING INTO THE NORTHERN PLAINS OVER THE
WEEKEND. THIS WAVE IS FORECAST TO SWING ACROSS THE GREAT LAKES AND
RE-ESTABLISH THE EASTERN U.S TROUGH BY MONDAY.

LOOKS LIKE WE SHOULD BE ABLE TO SQUEEZE OUT ONE MORE NICE DAY ON
SATURDAY BEHIND THE THURSDAY FRONTAL PASSAGE AS HIGH PRESSURE
REMAINS WEEKLY RIDGED OVER THE AREA AND MOISTURE LEVELS REMAIN
RELATIVELY LOW. HOWEVER...IT LOOKS LIKE THE FIRST PART OF NEXT
WEEK WILL TURN STORMY. ALL THE MEDIUM RANGE MODELS HINT AT A
POSSIBLE MCS MAKING A RUN AT THE SOUTHERN APPALACHIANS ON SUNDAY. IT
IS DIFFICULT TO SAY WHETHER ANY OF THE PARENT STORMS WILL MAKE IT
ACROSS THE MOUNTAINS...BUT THE OUTFLOW MAY TRIGGER ADDITIONAL STORMS
ACROSS THE PIEDMONT SUNDAY AFTERNOON AND NIGHT. ALSO..AS THE UPPER
TROUGH DIGS OVER THE GREAT LAKES EARLY NEXT WEEK A COLD FRONT IS
FORECAST TO ARRIVE ON MONDAY PROVIDING THE TRIGGER FOR MORE
THUNDERSTORMS. SEVERE STORMS ARE A POSSIBILITY FROM SUNDAY INTO
MONDAY.

THE FRONT IS FORECAST TO CLEAR THE AREA MONDAY NIGHT WHICH SHOULD
ALLOW FOR DRYER AND MORE STABLE AIR TO OVERSPREAD THE AREA FROM THE
NW ON TUESDAY. MAX TEMPS ARE FORECAST TO BE NEAR OR EVEN SLIGHTLY
ABOVE CLIMO SAT THROUGH MONDAY...AND THEN BELOW CLIMO ON TUE BEHIND
THE COLD FRONT

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AT KCLT... EXTENSIVE CLOUD COVER WILL CONTINUE ACROSS THE AERODROME
AND VICINITY INTO THE EVENING... HOWEVER THE EARLIER STRATUS LAYER
HAS EVOLVED INTO A CUMULUS AND STRATOCUMULUS CLOUD FIELD WITH BASES
NEAR 4K FT. VISIBILITY WILL REMAIN UNRESTRICTED EXCEPT IN SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS PRIMARILY BETWEEN 21Z AND 00Z.
OVERNIGHT CONVECTIVE CLOUDS WILL DIMINISH AND GIVE WAY TO MORE
STRATIFORM SCATTERED TO BROKEN CLOUD WITH BASES 1-2K FT. OVERNIGHT
VISIBILITY WILL LOWER TO NEAR 5 MILES IN FOG AND HAZE VICINITY
KCLT... BUT CONFIDENCE NOT YET SUFFICIENT TO FORECAST SIGNIFICANT
RESTRICTIONS TOWARD DAYBREAK. NEITHER THE NAM MOS OR NGM MOS
INDICATE A PROLONGED PERIOD OF LOW CEILING OR VISIBILITY AT THIS
TIME. LATEST GFS LAMP POINTS TOWARD MVFR CEILING AND VISIBILITY FROM
09Z TO 12Z. AFTER 13Z WEDNESDAY... VISIBILITY WILL BECOME
UNRESTRICTED SURFACE HEATING WILL PRODUCE CUMULUS CLOUDS WITH BASES
NEAR 4K FT.

ELSEWHERE... CUMULUS AND STRATOCUMULUS CLOUD BASES 3-5K FT WILL
PERSIST INTO THE EVENING. NO RESTRICTIONS EXCEPT IN SCATTERED RAIN
SHOWERS AND ISOLATED THUNDERSTORMS THROUGH APPROXIMATELY 02Z.
OVERNIGHT... CONVECTIVE CLOUD WILL EVOLVE TO SCATTERED TO BROKEN
STRATUS WITH BASES 1-2K FT. AREAS OF FOG WITH VISIBILITY NEAR 1 MILE
MOST LIKELY AT KAVL. AFTER 14Z VISIBILITY WILL BECOME UNRESTRICTED
AND SURFACE HEARING WILL PRODUCE CUMULUS CLOUDS WITH BASES NEAR 4K
FT.

OUTLOOK... SHOWERS AND THUNDERSTORMS THURSDAY WITH THE PASSAGE OF A
COLD FRONT THURSDAY. SCATTERED SHOWERS AND THUNDERSTORMS MAINLY
DURING THE AFTERNOONS AND EVENINGS THROUGH THE END OF THE WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  99%     HIGH  85%     MED   66%     HIGH  87%
KGSP       HIGH  83%     MED   63%     MED   63%     HIGH  94%
KAVL       MED   62%     MED   64%     MED   71%     MED   71%
KHKY       HIGH  81%     MED   78%     MED   68%     HIGH  95%
KGMU       HIGH  83%     MED   63%     MED   70%     HIGH  90%
KAND       HIGH  91%     MED   77%     MED   66%     MED   71%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...PM
NEAR TERM...LGL
SHORT TERM...LG
LONG TERM...LG
AVIATION...LGL






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